Modeling investigation of membrane biofouling phenomena by considering the adsorption of protein, polysaccharide and humic acid

The importance of solute adsorption in the biofouling membrane has been clearly verified for the performance of membrane bioreactor (MBR). In order to quantify the mechanism of static adsorption in biofouling during of MBR process, we characterize membrane biofouling caused by model solutions containing a protein (bovine serum albumin, BSA), a humic substance (humic acid, HA) and a polysaccharide (alginic acid, Alg) on commercial hydrophilic polyethersulfone (PES) membrane. For static adsorption experiments, membranes were immersed in well-defined model solutions in three temperatures (298, 308 and 318 K) to obtain equilibrium data. To determine the characteristic parameters for this process, 7 isotherm models were applied to the experimental data. Three error analysis methods; the coefficient of nonlinear regression (R2), the sum of the squared errors (SSE) and standard deviation of residuals (Syx), were used to evaluate the data and determine the best fit isotherm for each model solutions. The error values demonstrated that the Sips isotherm model provided the best fit to the experimental data. AFM images were used for determination of changes in membrane surface after adsorption. These images confirmed the results obtained from adsorption isotherm study. Thermodynamic parameters such as standard free energy (ΔrGθ), enthalpy (ΔrHθ) and entropy (ΔrSθ) changes were determined; these adsorption processes were found to be feasible and endothermic but not spontaneous. The distribution of the substances adsorbed on PES surface were more chaotic than that in the aqueous solutions. Parameters obtained in this study can be used to determine the “fouling potential” of a given feed stream and a membrane.

. The Sips- or Langmuir–Freundlich-isotherm equation provide the closest fit to the equilibrium data for adsorption of protein, polysaccharides and humic acid on hydrophilic PES membrane. These results present fundamental information for a better understanding of biofouling by these model foulants.Figure optionsDownload as PowerPoint slideHighlights
► The adsorption of polysaccharide on PES microfiltration membrane was studied.
► The adsorption processes were feasible and endothermic.
► AFM image showed that the adsorption pattern of protein and humic acid are similar.
► Error analysis was done to determine the best isotherm model.
► The Sips isotherm was found to provide the best fit to the data.